Witnesses said the boy had scavenged flammable powder from discarded and unused personal fireworks he found in the neighborhood, and he put the volatile mix into a cardboard tube on a fireworks ground display, Humphrey said.

The boy was transported in critical condition to St. Mary Medical Center in Long Beach for emergency trauma care, after which he was transferred by private ambulance to a regional burn center, Humphrey said.

"The folks at St. Mary did a terrific job stabilizing him," Humphrey said. "He's going to be getting hands-on care for days and days."